Parkinson’s disease may start in the appendix, not the brain. People are less likely to get the condition if they had their appendix out decades previously. And a toxic compound found in the brains of people with this disease has now been spotted in the appendix.
Parkinson’s, a degenerative condition involving tremors and stiffness, has long been thought to stem from the death of brain cells, caused by build up of a protein called synuclein that normally plays a role in nerve signalling.
In people with Parkinson’s, synuclein is found in clumps that kill off nerve cells in parts of the brain controlling movement. When synuclein starts to aggregate in one place, the clumping spreads along nerves in a chain reaction.
Evidence has been growing that this process may begin in nerves of the gut. For instance, if clumped synuclein is injected into the gut of mice, the toxic aggregates spread to their brains.
Some previous studies have singled out the appendix as a key player in the onset of Parkinson’s. But research exploring whether having your appendix out protects against Parkinson’s has given contradictory results. The operation seems to be linked with a short-term slightly increased risk of the condition, but a lower risk over the longer term.
So Viviane Labrie of the Van Andel Research Institute in Michigan, tackled the question with the largest and longest study to date, looking at the healthcare records of 1.6 million Swedish people over 52 years. Those who’d had their appendix out as young adults had nearly a 20 per cent lower chance of developing Parkinson’s in later life.
Labrie’s team also looked at 48 appendixes taken from people with and without Parkinson’s and found that in nearly all there was clumped synuclein in the organ’s nerve fibres. This “could act as a seed for the disease in the brain,” says Labrie.
But it’s still unknown why this only happens in some people.